Wireless communication devices are used, in general, to connect wirelessly to a network. Reliable operation of modern wireless communication devices often requires knowledge of characteristics such as the power or magnitude of signals transmitted by that device. This could be required for compliance with a given communication scheme or for increasing the power efficiency of a wireless communication device. Such knowledge could be used, for example, to modify power control, radiated power variation, power amplifier control, antenna tuner control, etc.
It is often not sufficient to calculate the characteristics of a transmitted signal by examining the signal data prior to transmittal. This could be due to unknown efficiency values, temperature effects, frequency dependency, impedance mismatches, and/or nonlinear properties of subsequent transmitter path components. In order to accurately determine the transmitted signal characteristics, it is known in the art to provide a measurement receiver at the wireless communication device in order to measure the signal immediately prior to transmission. Several measurement receiver arrangements are known in the art. For example, a resistor arrangement can be used prior to the antenna to divide resistively the signal between the antenna and a detector, such as a power detector. The output of the power detector can then be integrated to obtain a value proportional to the transmitted power over the measurement period, and further divided by the length of the measurement period in order to determine an average power value.
In order to operate a measurement receiver in such a way as to reflect accurately the power of the transmitted signal, several prior art arrangements require the transmitted signal to be measured over a relatively long period of time. This has the effect of mitigating the chance of measuring only an unusually high or low powered portion of the signal. The measurements made over this relatively long measurement period can then be averaged to obtain a value for the transmitted signal power over the same period. However, during operation, the measurement receiver is a current consuming component and hence operating the measurement receiver for a relatively long period of time consumes undesirable amounts of current. This is a particular problem for mobile wireless communication devices, where battery life is limited and current consumption should be constrained.
In other known measurement receiver arrangements, a coupler is used prior to the antenna to monitor the signal and can be used to determine both forward and reflected power. Forward power is typically measured via a first port on the coupler and power reflected from the antenna is measured via a second port on the coupler. These measurements can be used to determine the difference or ratio between forward and reflected power. However, again, long measurement periods are required for accurate readings, and this is compounded by the requirement to separately measure both forward and reflected power during the same transmission.
Further known measurement receiver arrangements provide precise synchronisation between the measured signal and the data components of the transmitted signal through the use of correlating logic. This type of measurement receiver arrangement is known as a fully coherent receiver and allows for single measurement samples to be utilised through precise phase correlation. In this way, the presence of the various peaks and troughs in the transmitted signal can be accurately predicted and the measured value can be scaled accordingly to determine the characteristics of the transmitted signal. However, such fully coherent measurement receiver arrangements require a significant amount of correlation logic which increases hardware complexity and cost. Additionally, as there is no averaging of the signal envelope, such arrangements do not determine average power, only analogue gain and phase.
Hence, it would be desirable to provide improved measures for determining characteristics of a signal transmitted from a wireless transmitter, including measures with reduced power consumption and/or hardware complexity.